The present disclosure relates to an electrophotographic image forming apparatus, an optical scanning device provided in an image forming apparatus, and an optical scanning method implemented in an optical scanning device.
In an image forming apparatus such as a printer that can form an image by the electrophotographic system, a light beam emitted from a light source based on image data is caused to scan an image carrying member such as a photoconductor drum by a rotary polygon mirror, so that an electrostatic latent image corresponding to the image data is formed on the image carrying member. In this type of image forming apparatus, an emission timing at which a light beam corresponding to each line of the image data is emitted, namely, a timing to write the electrostatic latent image is determined based on a detection timing at which a light receiving portion detects a light beam emitted from the light source and scanned by the rotary polygon mirror.
In addition, in this type of image forming apparatus, a reflection surface of the rotary polygon mirror may be stained. In that case, the reflectance of the reflection surface is reduced, and thereby the light amount of the light beam that is scanned by the rotary polygon mirror is reduced. With regard to this problem, there is known an image forming apparatus that can adjust the light emission amount of the light source based on the light amount of the light beam detected by the light receiving portion.